Gravure printing process and apparatus using moisture-setting inks

ABSTRACT

A PRINTING PROCESS AND APPARATUS WHEREIN A GRAVURE PRINTING PRESS IS PROVIDED WITH A PRESSURE DRYING UNIT TO SET A MOISTURE-SETTING INK THAT PREVIOUSLY HAS BEEN MODIFIED BY THE ADDITION OF GLYCOL AND WATER TO THE INK FORMULATION TO RESPECTIVELY REDUCE THE VISCOSITY OF THE INK AND ENHANCE ITS SENSITIVITY TO WATER BY BRINGING IT SUBSTANTIALLY TO THE THRESHOLD OF PRECIPITATION. THE DRYING UNIT DAMPENS AND SETS THE INK BY SUPPLYING THE ADDITIONAL WATER NECESSARY TO PRECIPITATE THE RESIN IN THE INK FORMULATION AND FORCES THE WATER-GLYCOL BLEND INTO THE WEB STOCK BEING PRINTED. THE ADVANTAGES OF GRAVURE PRINTING ARE THUS OBTAINED WITHOUT USE OF THE TOXIC AND FLAMMABLE INKS HERETOFORE, REQUIRED WITH THE GRAVURE PROCESS.

S p 1972 M. J. TINGHITELLA ETAL 3,

GRAVURE PRINTING PROCESS AND APPARATUS USING MOISTURE-SETTING INKS Filed March 4, 1968 INVENTORS MICHAEL J. TINGHI'TELLA KENNETH E. R N

United States Patent Patented Sept. 26, 1972 ABSTRACT OF THE DISCLOSURE A printing process and apparatus wherein a gravure printing press is provided with a pressure drying unit to set a moisture-setting ink that previously has been modified by the addition of glycol and water to the ink formulation to respectively reduce the viscosity of the ink and enhance its sensitivity to water by bringing it substantially, to the threshold of precipitation. The drying unit dampens and sets the ink by supplying the additional water necessary to precipitate the resin in the ink formulation and forces the water-glycol blend into the Web stock being printed. The advantages of gravure printing are thus obtained without use of the toxic and flammable inks heretofore required with the gravure process.

BACKGROUND OF INVENTION This invention relates to processes and apparatus for printing on paper or other fibrous web stock, and more particularly to a gravure printing process and apparatus employing an improved, highly fluid moisture-setting ink and a pressure drying unit.

In gravure printing, a gravure plate cylinder is used having image areas defined by patterns of closely spaced etched pin holes. The cylinder is rotated partially immersed in a trough containing a fluid ink. As the cylinder is rotated past a doctor blade pressed against its periphery, the ink is scraped off the cylinder except in the image areas defined by the pin hole patterns. This scraping or wiping occurs just before the cylinder periphery contacts a rubber impression roll. As a web of paper or other stock to be printed upon passes through the nip formed by the impression roll and plate cylinder, the ink is picked out of the etched image areas.

Gravure printing has many advantages. For example, no long and complicated ink trains are required. Very volatile and fluid inks are used that are capable of rapid drying by evaporation. Also, thicker ink films and higher resolution and print quality are obtainable than with other forms of printing, such as letterpress or lithography. However, gravure printing presses heretofore proposed have one serious disadvantage; viz., they employ inks that are highly toxic and flammable, requiring expensive exhaust sy'stems'and safety precautions to reduce the threat to health and hazard of fire.

Moisture-setting inks have been used for years in letterpress printing when rapid setting is desired. Moisturesetting inks are 'safe but they are very thick, having a consistency like that of putty. Basically, moisture-setting inks are composed of high-acid-number resins, usually highly fumarated or maleized rosins, dissolved in a high boiling glycol, such as diethylene glycol. The pigments chosen must be either neutral or acidic in character to prevent reaction with the resin. Other additives such as waxes and stabilizing agents are generally included, but these are not pertinent to the present invention and hence need not be discussed. The resin is chosen so that it is soluble in glycols but insoluble in glycol-water mixtures. Consequently, when such an ink is printed, a portion of the glycol solvent will be absorbed into the stock through capillary action, leaving a concentrated resin-pigment-solvent mixture on the surface of the paper. When this surface encounters an environment of high moisture content (usually in the form of steam), the hygroscopic solvent will absorb water, thereby precipitating the resin and binding the pigment to the web stock. The residual glycol-water mixture then penetrates the stock leaving a dry ink film.

Letterpress printing has a number of disadvantages, however. For example, it provides only thin ink films. Print quality and resolution are relatively poor; and long and complicated ink train roll systems are required.

SUMMARY OF INVENTION The principal object of this invention is to achieve the above-enumerated advantages of gravure printing without requiring the toxic and highly flammable inks heretofore proposed and without any of the disadvantages of letterpress printing.

Toward this end, and according to the invention, a gravure press employing a conventional gravure plate cylinder and doctor blade is modified by addition of a pressure drying unit of the type proposed in US. Pat. 3,302,296 to -R. H. Holmwod et al. for use in a letterpress or dry offset printing apparatus. Also, a moisturesetting ink is employed which is modified by the addition of glycol to so reduce its viscosity that it may be used with an etched gravure plate cylinder, and further modified by the addition of water in an amount necessary to bring it substantially to the threshold of precipitation.

Other objects and advantages wil become apparent from the following more detailed description of the invention and from the accompanying drawing, wherein the single figure is a schematic elevational view of a gravure printing press embodying the invention.

DETAILED DESCRIPTION OF INVENTION As illustrated in the drawing, a web 10 of paper stock is advanced upwardly by and between a pair of suitably driven guide rolls 11, 11' around a deflecting roll 12, and then between a gravure plate cylinder 13 and rubber impression roll 14 at a printing station, designated generally 15.

Plate cylinder 13 is of conventional form having image areas defined by patterns of closely spaced etched pin holes. A suitably driven shaft 16 rotates cylinder 13 while the latter is partially immersed in a novel moisture-settink ink 17 (hereinafter to be described) contained in a trough 18. A conventional stationary doctor blade 19 pressed against the periphery of cylinder 13 scrapes the ink off the cylinder except in the image areas defined by the ink cells provided by the etched pin hole patterns, to cause the ink to be picked out of these ink cells and transferred to web 10 as the latter passes through the nip between the gravure plate cylinder 13 and rubber impression roll 14.

After leaving the print station 15, web 10 is advanced upwardly by and between pressure rolls 20, 21 forming part of a pressure drying station 22. At this station, upstream of rolls 20, 21, are a dampening roll 23, a metering roll 24, and a spray applicator 25. Moisture under pressure is supplied from a suitable source (not shown) via a conduit 26 to applicator 25, which directs a stream onto the soft, moisture-retaining surface of a dampening roll 23. Metering roll 24 has a hard hydrophilic surface and is mounted so as to be adjustable toward and away from roll 23 to regulate the amount of moisture retained by the dampening roll. Dampening roll 23 rotates in contact with the hydrophilic surface of roll 20 to assure that the thin film of moisture transferred thereto from the dampening roll will be spread uniformly and evenly over the entire surface without forming droplets.

Thus, after ink is transferred to web from the ink cells in gravure plate cylinder 13, the web with ink in wet condition is advanced past spray applicator 25 which adds sufiicient moisture to expedite setting or drying of the ink. The web then passes through the nip of rolls 20, 21 which exert a high nip pressure on the web. Since pressure roll 20 has a uniformly hydrophilic surface, this moistened surface constitutes a barrier assuring prompt release of the ink from said roll at the nip exit.

Conventional moisture-setting inks have a viscosity of approximately 2000 to 3000 poise, and thus have a consistency like that of putty; whereas gravure inks are considerably thinner, having a viscosity of the order of .1 to .5 poise.

According to the invention, conventional moisture-setting inks are modified in a manner which enables them to be successfully used on gravure presses. This modification involves the addition of glycols to the ink formulation to substantially reduce its viscosity. However, as glycol is added, the sensitivity of the moisture-setting ink is undesirably reduced; and this will undesirably increase the amount of time necessary for the ink to set and thus impractically increase the web travel required for setting the ink and/or decrease the printing throughput of the press. To overcome this drawback, the ink formulation is further modified by the addition of sufiicient water to bring the ink formulation up substantially to the threshold of precipitation and restore the sensitivity of the ink to water. The time required for setting or drying the moisture-setting ink is further reduced by the addition to the gravure press of the pressure drying station 22 which provides the moisture transfer, high nip pressure and requisite ink release that greatly speed up drying of the ink by supplying the water necessary to precipitate the resin in the ink and also force the water-glycol blend into the web.

It should be noted that the degree of reduction in viscosity depends upon the throughput speed of the gravure press. Thus, for a high-speed press, enough glycol should be added to reduce the viscosity to about .1 to .5 poise; whereas for a slow-speed press, the viscosity could be as much as 50 poise.

Also, for the particular resin-glycol mixture, the threshold of precipitation preferably is determined by titrating the mixture in a laboratory environment until irreversible precipitation occurs. Then, knowing the amount of water that has been added, the formulation by weight is calculated; whereupon, for actual press operation, the amount of water would be reduced to between 80 and 95% of that which produced irreversible precipitation, dependingupou the type of press used. For example, for presses having large ink rolls, the amount of water added would be less than for those with small ink rolls. This is because as the rolls rotate after leaving the ink trough, the glycol in the ink formulation will absorb moisture from the ambient air; and the larger the ink roll, the longer its ink-coated surface will be exposed to the air before printing on the web 10. The term substantially to the threshold of precipitation as herein used is intended to embrace ink formulations containing approximately 80% or more of the amount of water necessary to cause irreversible precipitation of the resin in that particular ink formulation.

Moisture-setting inks modified according to the invention comprise a transparent or colored pigment, which may be basic, but preferably is neutral or acidic. These inks also comprise high-acid-number resins, usually highly fumarated or maleized rosins, dissolved in a high-boiling-point glycol, such as diethylene glycol, but insoluble in glycol-water mixtures.

The following are examples of moisture-setting ink formulations that have been successfully printed and dried using a gravure press modified according to the invention. All formulations are by weight.

Example 1 Material: Percent Surfex M M (Ca CO 20 50% FCD-SO in triethylene glycol (partially esterified fumarated rosin of France, Campbell and Darling Company) 60 Triethylene glycol 15 Water 4 Tergitol NPX (ethoxylated nonyl phenol of Union Carbide Corp.) 1

Example 2 Material: Percent Surfex M M 50 50% FCD-SO in triethylene glycol (see above) 30 Ethylene glycol 15 Water 3 Tergitol NP-27 (see above) 2 Example 3 Material: Percent Surfex M M 30 50% FCD-SO in diethylene glycol 30 Diethylene glycol 30 Water 8 Atlas G-67Z (polyoxyethylene alcohol of Atlas Chemical Industries, Inc.) 2

The ink formulations specified in Examples 1, 2 and 3 were employed in a transparent functional coating applied to card stock to enhance its abrasiveness to a marksense pencil. However, if desired, a conventional colored pigment or carbon black may be substituted for the calcium carbonate in each example to provide a conventional, non-abrasive colored ink coating. The colored pigment may be basic, neutral or acidic, depending on the resin solution chosen.

The following are additional examples of moisture-setting ink formulations that could be applied by gravure techniques, for example as an aesthetic background tint coating for checks.

Example 4 Material: Percent Cyanadur Violet 55-8500 1 50/50 FCD-16 in diethylene glycol (high-acidnumber fumarated rosin of France, Campbell and Darling Company) 60 Triethylene glycol 30 Water I 8 Sotex 3CW (monoester of a polyglycol of Synthetic Chemicals, Inc.) 1

Example 5 Cyanadur Violet ss-ssoo 10 50%! Chanco 659 in diethylene glycol (modified polyester of Shanco. Plastics and Chemicals,

Inc.) 30 'Ethylene glycol 50 Water 8 Tergitol NP-27 (see above) 2 Example 6 Primrose Chrome Yellow 40 Iron Blue BA-9146 3 50/50 FCDr-l6 in triethylene glycol 30 Diethylene glycol 20 Water 6 Tergitol NP-27 (see above) 1 In each of these formulations according to Examples 4, 5 and 6 other substantially neutral colored pigments could be substituted. Also the percentage by weightof such pigments could be varied depending upon the intensity of colored ink coating or image desired.

Resins which predominantly contain abietic acid and/ or its esters are believed preferable. However, it will be apparent that, if desired, other commercially available naturally occurring resin acids or synthetic polymeric materials may be used which possess the property of solvency in glycols but insolubility in glycol-aqueous blends. It will also be apparent that many commercially available glycol solvents, wetting agents, and pigments may be substituted for those specified in the foregoing examples without departing from the spirit, scope and teachings of the present invention. Accordingly, the examples are to be considered merely as illustrative, and the scope of the invention is to be limited only as specified in the claim.

What is claimed is:

1. For use with a gravure plate cylinder rotatable through an ink trough for transferring ink to stock to be printed upon, and means for supplying moisture to the stock after such transfer for setting the ink, a moisturesetting ink comprising a pigment;

a resin from the class of resins containing abietic acid or its esters;

glycol in a quantity sufi'icient to render the ink fluid References Cited UNITED STATES PATENTS Horton 101-157 Weiss 101-416 Voet 106-30 Ireton 101-416 Miller et a1 10630X Holmwood et al 34-9 JOAN B. EVANS, Primary Examiner US. Cl. X.R. 

